1. Field of the Invention
The invention generally relates to heart rate monitors for use in association with exercising equipment. In particular, the invention relates to a two electrode monitor employing digital signal processing of signals detected by the electrodes.
2. Description of the Prior Art
Heart rate monitors for use with exercise equipment are known in the art. In general, such monitors tend to require four electrodes, two for each hand, in order to accurately detect a beat to beat heart rate. Some patented prior art monitors include the following. U.S. Pat. No. 3,702,113 illustrates a heart rate monitor with only one electrode per hand. U.S. Pat. No. 5,243,993 discloses a heart rate monitor which includes a digital signal processor 44 for implementing autocorrelator 26, signal processor 28 and arbitrator 30. Similarly, Antii Ruha, Sami Sallinen & Seppo Nissila, in A Real-Time Microprocessor ORS Detector System with a 1-ms Timing Accuracy for the Measurement of Ambulatory HRV, IEEE Transactions on Biomedical Engineering, March 1997, teach the use of digital signal processing in connection with monitoring a patient's heart rate.
U.S. Pat. No. 5,337,753 is directed to a four-electrode (two electrodes per hand) heart rate monitor. Specifically, it calls for a first live electrode and a first common electrode mounted on one half of an elongate member in spaced relationship with each other and a second live electrode and a second common electrode mounted on the other half of the elongate member in spaced relationship with each other.
Referring next to U.S. Pat. No. 5,337,753, it discloses an apparatus for measuring heart rate having at least the following features: (i) sensor means for generating an input signal including the biopotential signal produced by the user's heart, (ii) autocorrelating means responsive to the input signal for periodically generating an autocorrelation signal of the input signal over a predetermined time period and (iii) signal indication means responsive to the autocorrelation signal for detecting the presence of at least one periodic signal in the autocorrelation signal and generating a heart rate signal corresponding to the detected signal(s).
U.S. Pat. No. 4,319,581 describes an apparatus having a first hand grip for attachment to one end of the handlebar of a bicycle or stationary exercise device, a second hand grip including a second means for electrically contacting the other end of said handlebar, third and fourth means disposed upon said second hand grip in spaced apart relationship and adapted to electrically engage said other hand of said user, and signal monitoring means for measuring electric pulses created in the body and for indicating the heart pulse rate of such body.
There is a need for a low cost, accurate monitor which digitally processes signals on a power spectrum basis rather than a peak to peak basis, which employs only two electrodes and which includes an isolation barrier.